util: uart_stress_tester checks if the given ports exist

During initialization, uart_stress_tester checks each of ports
exists, and raises an error if not.

BUG=None
BRANCH=None
TEST=ran on fleex.

$ uart_stress_tester.py /dev/ttyUSBX -t 120
Error:  [Errno 2] No such file or directory: '/dev/ttyUSBX'

$ ./util/uart_stress_tester.py ./util/uart_stress_tester.py -t 120
Error:  ./util/uart_stress_tester.py is not a character device.

Change-Id: I989a9e767796b04b059861aea2a3412877c1d739
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1706626
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/util/uart_stress_tester.py b/util/uart_stress_tester.py
index 2dd5e12515..13828fe84e 100755
--- a/util/uart_stress_tester.py
+++ b/util/uart_stress_tester.py
@@ -23,6 +23,8 @@ from chromite.lib import cros_logging as logging
 import argparse
 import atexit
 import serial
+import os
+import stat
 import sys
 import threading
 import time
@@ -381,10 +383,20 @@ class ChargenTest(object):
       ports: List of UART ports to test.
       duration: Time to keep testing in seconds.
       cr50_workload: True if a workload should be generated on cr50
+
+    Raises:
+      ChargenTestError: if any of ports is not a valid character device.
     """
 
     # Save the arguments
     self.ports = ports
+    for port in ports:
+      try:
+        mode = os.stat(port).st_mode
+      except OSError as e:
+        raise ChargenTestError(e)
+      if not stat.S_ISCHR(mode):
+        raise ChargenTestError('%s is not a character device.' % port)
 
     if duration <= 0:
       raise ChargenTestError('Input error: duration is not positive.')